Impeller and rotary machine

ABSTRACT

An impeller includes: a disc portion fixed to a rotary shaft that rotates around an axis line; a cover portion disposed to face the disc portion; and a plurality of blade portions provided between the disc portion and the cover portion. The impeller includes a first segment configured of a first disc portion that is a portion of the disc portion on one side of the axis line, a second segment in which a second disc portion that is a portion of the disc portion on another side of the axis line, the cover portion, and the blade portions are integrally configured, and a bonding layer configured to bond the first disc portion of the first segment and the second disc portion of the second segment with a bonding agent.

TECHNICAL FIELD

The present invention relates to an impeller used in a rotary machine.

BACKGROUND ART

For example, a rotary machine such as an industrial compressor, a turbo refrigerator, and a small gas turbine includes an impeller in which a plurality of blades are attached to a disc fixed to a rotary shaft. The rotary machine applies pressure energy and speed energy to gas through rotation of the impeller.

As the impeller, a so-called closed impeller in which a cover is integrally attached to the blades has been well-known. The closed impeller includes an impeller assembled by bonding a plurality of members. The impeller including such a bonding structure tends to be reduced in performance of the impeller because of low quality of a flow path shape. Patent Literature 1 proposes to configure the impeller as a single piece in order to address the issue.

In Patent Literature 1, in the impeller including a disc portion, blade portions, and a cover portion, the disc portion includes a first member (first segment) and a second member (second segment) that are divided at a division surface orthogonal to an axis line inside the blade portion in the radial direction. Patent Literature 1 proposes to bond the first segment and the second segment at the division surface.

According to the proposition by Patent Literature 1, it is possible to improve the quality of the flow path shape and to easily attach/detach the impeller with respect to the rotary shaft.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2015-101967 A

SUMMARY OF INVENTION Technical Problem

In Patent Literature 1, the first segment and the second segment are bonded at the division surface by brazing or friction stir welding. The bonding method is based on the premise that the first segment and the second segment in Patent Literature 1 are each made of a metal material. In other words, in Patent Literature 1, a choice of the material to be applied to the first segment and the second segment is limited.

Accordingly, an object of the present invention is to provide an impeller and a rotary machine that make it possible to expand a range of choices of a material to be applied to the first segment and the second segment.

Solution to Problem

An impeller according to the present invention includes a disc portion fixed to a rotary shaft that rotates around an axis line, a cover portion disposed to face the disc portion; and a plurality of blade portions provided between the disc portion and the cover portion.

The impeller according to the present invention includes a first segment configured of a first disc portion that is a portion of the disc portion on one side of the axis line; a second segment in which a second disc portion that is a portion of the disc portion on another side of the axis line, the cover portion, and the blade portions are integrally configured; and a bonding layer configured to bond the first disc portion of the first segment and the second disc portion of the second segment with a bonding agent.

In the impeller according to the present invention, the first disc portion of the first segment and the second disc portion of the second segment are bonded with the bonding agent. Accordingly, the range of choices of the material of the first segment and the second segment is expanded to include a fiber-reinforced plastic without being limited to a metal material. In other words, in the impeller according to the present invention, the first segment can be made of a metal material or a fiber-reinforced plastic, and the second segment can be made of a metal material or a fiber-reinforced plastic.

In the impeller according to the present invention, the first segment can be made of a metal material, and the second segment can be made of a fiber-reinforced plastic, as a specific choice of the material.

Further, in the impeller according to the present invention, both of the first segment and the second segment can be made of a fiber-reinforced plastic.

Further, in the impeller according to the present invention, both of the first segment and the second segment can be made of a metal material.

The impeller according to the present invention can be fixed to the rotary shaft through the first disc portion of the first segment.

In a case where the first segment is made of a metal material, the first segment can be fitted to the rotary shaft with an interference.

In a case where the first segment is made of a fiber-reinforced plastic, the first segment can be fitted to the rotary shaft with a bonding agent.

In the impeller according to the present invention, in a case where both of the first segment and the second segment are made of a metal material, a film made of metallic salt is preferably provided on a surface on which the bonding layer is to be provided.

Further, in the impeller according to the present invention, a mechanical fitting structure is preferably provided between the first disc portion of the first segment and the second disc portion of the second segment.

The present invention also provides a rotary machine including any of the above-described impellers.

Advantageous Effects of Invention

In the impeller according to the present invention, the first segment and the second segment are bonded with the bonding agent layer. Thus, according to the present invention, the material configuring the first segment and the second segment is selectable without being limited to a metal material, which expands the range of material choices. Therefore, for example, the fiber-reinforced plastic that is lower in weight than the metal material can be used for the first segment or the second segment. Thus, according to the present invention, it is possible to reduce the weight of the impeller as compared with a case where the impeller is wholly fabricated from a metal material.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view illustrating a centrifugal compressor according to a first embodiment of the present invention.

FIG. 2 is a perspective view illustrating an impeller according to the first embodiment.

FIG. 3 is a half cross-sectional view illustrating the impeller according to the first embodiment.

FIGS. 4A to 4C are cross-sectional views illustrating a procedure of manufacturing the impeller according to the first embodiment.

FIG. 5 is a flowchart illustrating the procedure of manufacturing the impeller according to the first embodiment.

FIG. 6 is a cross-sectional view illustrating an impeller according to a second embodiment.

FIGS. 7A to 7C are cross-sectional views illustrating a procedure of manufacturing the impeller according to the second embodiment.

FIG. 8 is a flowchart illustrating the procedure of manufacturing the impeller according to the second embodiment.

FIGS. 9A and 9B are cross-sectional views illustrating an impeller according to a modification of each of the first embodiment and the second embodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment

A centrifugal compressor 100 that is an example of a rotary machine according to a first embodiment of the present invention is described below with reference to accompanying drawings.

Configuration of Centrifugal Compressor 100

As illustrated in FIG. 1, the centrifugal compressor 100 according to the first embodiment includes a casing 102 and a rotary shaft 101 that is supported by the casing 102 through a journal bearing 103 and a thrust bearing 104. The rotary shaft 101 is supported so as to be rotatable around an axis line O, and a plurality of impellers 1 that are arranged in the axis line O direction are attached to the rotary shaft 101.

As illustrated in FIG. 2, each of the impellers 1 compresses gas G that is sucked from a suction port 3 while the gas G passes through a flow path 105 provided inside the impeller 1. The suction port 3 opens on one side in the axis line O direction. Each of the impellers 1 discharges the compressed gas G from a discharge port 4 toward outside in a radial direction.

The impellers 1 use centrifugal force derived from rotation of the rotary shaft 101 to stepwisely compress the gas G supplied from the flow path 105 on upstream side provided in the casing 102, and cause the compressed gas G to flow toward the flow path 105 on downstream side.

As illustrated in FIG. 1, the casing 102 includes, on front side (F) in the axis line O direction of the rotary shaft 101, a suction port 106 to take in the gas G from the outside. Further, the casing 102 includes, on rear side (R) in the axis line O direction, a discharge port 107 that causes the gas G to flow out to the outside.

In the centrifugal compressor 100, when the rotary shaft 101 rotates, the gas G flows into the flow path 105 from the suction port 106, the gas G is stepwisely compressed by the impellers 1, and the compressed gas G is discharged from the discharge port 107. FIG. 1 illustrates an example in which six impellers 1 are provided in series on the rotary shaft 101; however, it is sufficient to provide at least one impeller 1 on the rotary shaft 101. Note that, in the following description, a case where only one impeller 1 is provided on the rotary shaft 101 is described as an example, to simplify the description.

Configuration of Impeller 1

As illustrated in FIG. 2 and FIG. 3, the impeller 1 includes a disc portion 30, blade portions 40, and a cover portion 50.

The disc portion 30 is attached to the rotary shaft 101 by being fitted to the rotary shaft 101 from outside in the radial direction. As illustrated in FIG. 3, the disc portion 30 includes a first disc portion 31 and a second disc portion 35 that are divided in the axis line O direction at a bonding layer BL orthogonal to the axis line O. The first disc portion 31 and the second disc portion 35 are bonded with the bonding layer BL.

The first disc portion 31 includes a substantially cylindrical shape with the axis line O as a center. The first disc portion 31 includes, at the front end part 33 side on the front side (F) of the axis line O, a grip part A that is fitted to the rotary shaft 101 with an interference. At this time, to fit the first disc portion 31 to the rotary shaft 101 with the interference at the grip part A, cold fitting or shrink fitting is adoptable. The impeller 1 according to the present embodiment is fixed to the rotary shaft 101 at only the grip part A.

The first disc portion 31 includes an outer peripheral surface 34 that is gradually increased in diameter toward the rear side (R) of the axis line O. The outer peripheral surface 34 has a curved surface recessed outward in a cross-section including the axis line O.

A rear end surface 32 of the first disc portion 31 on the rear side (R) of the axis line O is bonded to the second disc portion 35 with the bonding layer BL containing a bonding agent.

The second disc portion 35 includes a disc shape that extends outward in the radial direction from a rear end part 36 side that is opposite to the front end part 33 side in the axis line O direction.

An inner-diameter-side region 38 on a front end surface 37 of the second disc portion 35 is bonded to the rear end surface 32 of the first disc portion 31 with the bonding layer BL. The rear end surface 32 and the inner-diameter-side region 38 of the front end surface 37 configure the bonding layer BL orthogonal to the axis line O.

An epoxy resin bonding agent, an anaerobic strong sealant, or the like is applied to the bonding layer BL. Note that, when the impeller 1 is assumed to be exposed to temperature of, for example, about 200° C., it is necessary for the bonding agent to be applied to have heat resistance of 200° C.

As illustrated in FIG. 2, the plurality of blade portions 40 are arranged at predetermined intervals in a circumferential direction of the disc portion 30.

As illustrated in FIG. 3, each of the blade portions 40 is formed to have a substantially constant plate thickness, and protrudes from the front end surface 37 of the disc portion 30 toward the front side (F) in the axis line O direction. Further, each of the blade portions 40 has a slightly tapered shape toward the outside in the radial direction in a side view.

As illustrated in FIG. 2, each of the blade portions 40 is formed so as to be directed to rear side in a rotation direction R of the impeller 1 as going toward the outside in the radial direction of the disc portion 30 as viewed from the axis line O direction. Further, each of the blade portions 40 is formed so as to be curved in a recessed shape toward the rear side in the rotation direction R as viewed from the axis line O direction. The example in which each of the blade portions 40 is curved as viewed from the axis line O direction has been described here; however, it is sufficient for each of the blade portions 40 to extend to the rear side in the rotation direction R as being closer to the outside in the radial direction. For example, each of the blade portions 40 may be linearly formed as viewed from the axis line O direction.

As illustrated in FIG. 3, the cover portion 50 is disposed to face the disc portion 30, and covers the blade portions 40 from the front end part 33 side in the axis line O direction.

A rear end surface 52 of the cover portion 50 in the axis line O direction is formed integrally with front side edges 41 of the respective blade portions 40. The cover portion 50 is formed in a plate shape in which a thickness dimension on the outside in the radial direction is slightly small, as with the thickness dimension of the disc portion 30. The cover portion 50 includes a bent part 51 that is bent toward the front side in the axis line O direction at positions of inside ends 42 of the respective blade portions 40.

The impeller 1 including the above-described configuration includes the bonding layer BL that is disposed on the inside in the radial direction of the blade portions 40. Further, the front end part 33 of the first disc portion 31 is disposed to protrude toward the front side (F) in the axis line O direction more than a front end edge 53 of the bent part 51. Moreover, in the impeller 1, the flow path 105 through which the gas G flows is formed by the outer peripheral surface 34 of the first disc portion 31, the front end surface 37 of the second disc portion 35, side surfaces 43 of the blade portions 40, and a rear end surface 52 of the cover portion 50.

The impeller 1 includes a first segment SG1 and a second segment SG2. The first segment SG1 includes the first disc portion 31 that is a portion of the disc portion 30 on one side of the axis line O. Further, the second segment SG2 includes the second disc portion 35 that is a portion of the disc portion 30 on the other side of the axis line O, the blade portions 40, and the cover portion 50.

In the impeller 1 according to the first embodiment, the first segment SG1 is made of a metal material such as precipitation hardening stainless steel, whereas the second segment SG2 is made of fiber-reinforced plastic (FRP). As the reinforcing fiber, for example, carbon fiber or glass fiber is used. In particular, carbon fiber-reinforced plastic (CFRP) that includes the carbon fiber as the reinforcing fiber is high in strength and elasticity and is excellent in corrosion resistance, as compared with the other FRPs.

Method of Manufacturing Impeller 1

Next, a method of manufacturing the above-described impeller 1 is described with reference to FIGS. 4A-4C and FIG. 5.

First, the first segment SG1 is fabricated by casting, cutting, or the like (FIG. 4A and step S101 in FIG. 5).

In addition, the second segment SG2 in which the second disc portion 35, the blade portions 40, and the cover portion 50 are integrated is fabricated (FIG. 4A and step S103 in FIG. 5). The second segment SG2 made of the fiber-reinforced plastic is integrally fabricated by injection molding.

Note that the first segment SG1 and the second segment SG2 are fabricated in this order for convenience; however, the first segment SG1 and the second segment SG2 may be fabricated in reverse order.

Next, the first segment SG1 (first disc portion 31) is fitted to and fixed to the rotary shaft 101 (FIG. 4B and step S105 in FIG. 5). The fitting can be performed by shrink fitting. In the shrink fitting, the first segment SG1 is heated to cause thermal expansion in the radial direction, and the thermally-expanded first segment SG1 is fitted to the rotary shaft 101. After the first segment SG1 is cooled to the room temperature, the first segment SG1 and the rotary shaft 101 are fitted to each other with an interference.

Next, a bonding agent B is applied on the rear end surface 32 of the first segment SG1 (first disc portion 31) fitted to the rotary shaft 101 and on the front end surface 37 (inner-diameter-side region 38) of the second segment SG2 (second disc portion 35) that has been separately fabricated (FIG. 4B and step S107 in FIG. 5). Note that the bonding agent B may be applied on any one of the rear end surface 32 and the front end surface 37.

After the bonding agent B is applied on the rear end surface 32 and the front end surface 37, the second segment SG2 is fitted to the rotary shaft 101 and is then pushed in until the rear end surface 32 of the first segment SG1 and the front end surface 37 abut on each other. The first segment SG1 and the second segment SG2 are held while a load is applied between the rear end surface 32 and the front end surface 37 until the bonding agent B is cured. As a result, bonding of the first segment SG1 and the second segment SG2 is completed (FIG. 4C and step S109 in FIG. 5).

Effects of First Embodiment

In the impeller 1, the first segment SG1 and the second segment SG2 are bonded with the bonding agent. As a result, a range of choices of the material to be applied to the second segment SG2 is expanded, and the second segment SG2 can be fabricated from the fiber-reinforced plastic that has a light weight as compared with a metal material. Accordingly, the weight reduction of the impeller 1 is achieved as compared with the case where the whole body is fabricated from a metal material. Thus, according to the present embodiment, it is possible to provide the high-efficiency centrifugal compressor 100.

In addition, in the impeller 1, the first disc portion 31 that is the first segment SG1 is made of the metal material. Therefore, the first disc portion 31 can be fitted to the rotary shaft 101 with necessary strength only by performing, for example, shrink fitting with an interference. Thus, the impeller 1 does not require a mechanical fitting structure such as a key and a key groove, which facilitates manufacture of the impeller 1.

In addition, the bonding layer BL formed by the bonding agent on each of the first segment SG1 and the second segment SG2 can be maintained through bonding of the rear end surface 32 and the front end surface 37 each on which the bonding agent has been applied, in the atmosphere. Accordingly, the first embodiment facilitates the bonding work as compared with brazing that uses heat treatment furnace in which temperature is controlled in vacuum.

In addition, in the case of the brazing, the work from charge of the impeller in the heat treatment furnace to completion of the brazing takes few days. In contrast, bonding with the bonding agent from application to curing takes only one day. Thus, according to the present embodiment, it is possible to manufacture the impeller 1 in a short time.

Further, the bonding with the bonding agent can be performed at ambient temperature without heating. Therefore, deformation of the impeller 1 due to heat does not occur. Thus, according to the present embodiment, it is possible to provide the impeller 1 with high accuracy in shape and dimension.

In addition, the bonding with the bonding agent is performable in the atmosphere. Therefore, the bonding condition is finely correctable before curing. Thus, the impeller 1 according to the present embodiment is higher in accuracy of the shape and the dimension.

Second Embodiment

Next, a second embodiment of the present invention is described.

An impeller 2 according to the second embodiment is different from the impeller 1 according to the first embodiment in that the first disc portion 31 configuring the first segment SG1 is also made of the fiber-reinforced plastic, in addition to the second segment SG2. The impeller 2 is described below with reference to FIG. 6 while focusing on differences with the impeller 1. Note that, in FIG. 6, configurations and components similar to those of the impeller 1 are denoted by the same reference numerals as the impeller 1.

In the impeller 2, the first disc portion 31 made of the fiber-reinforced plastic is fixed to the rotary shaft 101 with the bonding agent. To complement fixing strength by the bonding agent, in the impeller 2, the rotary shaft 101 and the first disc portion 31 respectively include key grooves S1 and S2, and a key K is inserted into the key grooves S1 and S2. The key grooves S1 and S2 and the key K can be provided, for example, at a part corresponding to the grip part A. A part between the rotary shaft 101 and the first disc portion 31 other than the part where the key grooves S1 and S2 and the key K are provided is bonded by the bonding agent B.

In the impeller 2, the first disc portion 31 is bonded to the rotary shaft 101 with the bonding agent at the grip part A. The second segment SG2 is bonded, with the bonding layer BL, to the first segment SG1 that includes the first disc portion 31 fixed to the rotary shaft 101 with the bonding agent. The bonding is similar to the bonding in the impeller 1 according to the first embodiment.

Method of Manufacturing Impeller 2

Next, a method of manufacturing the impeller 2 is described with reference to FIGS. 7A-7C and FIG. 8.

First, the first disc portion 31 configuring the first segment SG1 is fabricated by injection molding with use of the fiber-reinforced plastic (step S201 in FIG. 8). The key groove S2 is previously formed on an inner periphery of the first disc portion 31.

In addition, the second segment SG2 in which the second disc portion 35, the blade portions 40, and the cover portion 50 are integrated is integrally fabricated by injection molding with use of the fiber-reinforced plastic (step S203 in FIG. 8).

Next, the first segment SG1 (first disc portion 31) is fitted to the rotary shaft 101 (FIG. 7A and step S205 in FIG. 8).

The key groove S1 is previously provided in the rotary shaft 101 and the key K has been inserted into the key groove S1. In addition, the bonding agent B has been applied on the outer peripheral surface of the first disc portion 31 corresponding to the grip part A.

The first segment SG1 is fitted to the rotary shaft 101 such that the key K is inserted into the key groove S2. When the key K is pushed in until abutting on an innermost part of the key groove S2 (right side in figure), the fitting work of the first disc portion 31 and the rotary shaft 101 ends.

Note that the key K can be previously fixed to the key groove S1 of the rotary shaft 101 with the bonding agent.

Further, the fixing of the first disc portion 31 and the rotary shaft 101 with the bonding agent may be performed only at the part of the key grooves S1 and S2 and the key K as long as the bonding strength is sufficient.

The subsequent bonding of the first segment SG1 (first disc portion 31) and the second segment SG2 (second disc portion 35) with the bonding agent is similar to the bonding according to the first embodiment (FIG. 7C and steps S207 and S209 in FIG. 8).

Effects of Second Embodiment

The impeller 2 according to the second embodiment uses the first segment SG1 (first disc portion 31) made of the fiber-reinforced plastic. Thus, according to the second embodiment, further weight reduction of the impeller 2 is achieved, which makes it possible to provide the high-efficiency centrifugal compressor 100.

In addition, the second embodiment does not require heating to bond the first segment SG1 and the second segment SG2 to the rotary shaft 101. Therefore, the bonding work is easier than the bonding work in the first embodiment.

In addition, as compared with the case where the first disc portion 31 is fitted to the rotary shaft 101 by, for example, the shrink fitting, the time necessary for bonding of the first disc portion 31 and the rotary shaft 101 with the bonding agent is short. Thus, according to the second embodiment, it is possible to manufacture the impeller 2 in a time shorter than the first embodiment.

Although the preferred embodiments of the present invention have been described above, the configurations described in the above-described embodiments may be selected or appropriately modified in addition to the above description without departing from the scope of the present invention.

In the first embodiment and the second embodiment, at least one of the first segment SG1 and the second segment SG2 is fabricated from the fiber-reinforced plastic. The present invention, however, is not limited thereto, and both of the first segment SG1 and the second segment SG2 may be fabricated from a metal material. In other words, the present invention includes a choice in which the first segment SG1 is formed from a metal material or a fiber-reinforced plastic and the second segment SG2 is formed from a metal material or a fiber-reinforced plastic.

The present invention can adopt means for enhancing strength of the bonding between the first segment SG1 and the second segment SG2 with the bonding layer BL.

For example, in a case where both of the first segment SG1 and the second segment SG2 are made of an iron-based metal material, phosphate treatment can be performed on the rear end surface 32 and the front end surface 37 on which the bonding agent is to be applied. A thin film of metallic salt such as zinc phosphate with micron order is formed on the metal surface by the phosphate treatment. The surface is roughened because the film has a columnar shape, which increases the bonding strength of the bonding agent.

As the phosphate treatment, zinc phosphate treatment, calcium phosphate treatment, and iron phosphate treatment are well-known. The zinc phosphate treatment that is performable even at the ambient temperature is preferable.

Further, to enhance the bonding strength between the first disc portion 31 of the first segment SG1 and the second disc portion 35 of the second segment SG2, a mechanical fitting structure may be provided between the first disc portion 31 and the second disc portion 35.

For example, as illustrated in FIGS. 9A and 9B, a fitting structure 39 includes a recess 39A provided on the rear end surface 32 of the first disc portion 31 and a protrusion 39B provided on the front end surface 37 of the second disc portion 35. The protrusion 39B is inserted into the recess 39A to configure the fitting structure 39.

The fitting structure 39 is provided at each of four positions with an interval of 90 degrees in the circumferential direction of the first disc portion 31 and the second disc portion 35.

In addition, in the impellers 1 and 2 of the embodiments, a boundary surface between the first disc portion 31 and the second disc portion 35 extends along a direction orthogonal to the axis line O; however, the present invention is not limited thereto, and the boundary surface may be inclined with respect to the axis line O.

REFERENCE SIGNS LIST

-   1, 2 Impeller -   3 Suction port -   4 Discharge port -   30 Disc portion -   31 First disc portion -   32 Rear end surface -   33 Front end part -   34 Outer peripheral surface -   35 Second disc portion -   36 Rear end part -   37 Front end surface -   38 Inner-diameter-side region -   39 Fitting structure -   39A Recess -   39B Protrusion -   40 Blade portion -   41 Front side edge -   42 Inside end -   43 Side surface -   50 Cover portion -   51 Bent part -   52 Rear end surface -   53 Front end edge -   100 Centrifugal compressor -   101 Rotary shaft -   102 Casing -   103 Journal bearing -   104 Thrust bearing -   105 Flow path -   106 Suction port -   107 Discharge port -   A Grip part -   B Bonding agent -   BL Bonding layer -   K Key -   S1, S2 Key groove -   SG1 First segment -   SG2 Second segment -   O Axis line -   R Rotation direction -   G Gas 

1. An impeller, comprising: a disc portion fixed to a rotary shaft that rotates around an axis line; a cover portion disposed to face the disc portion; and a plurality of blade portions provided between the disc portion and the cover portion, wherein the impeller includes a first segment configured of a first disc portion that is a portion of the disc portion on one side of the axis line, a second segment in which a second disc portion that is a portion of the disc portion on another side of the axis line, the cover portion, and the blade portions are integrally configured, and a bonding layer configured to bond the first disc portion of the first segment and the second disc portion of the second segment with a bonding agent.
 2. The impeller according to claim 1, wherein the first segment is made of a metal material or a fiber-reinforced plastic, and the second segment is made of a metal material or a fiber-reinforced plastic.
 3. The impeller according to claim 1, wherein the first segment is made of a metal material, and the second segment is made of a fiber-reinforced plastic.
 4. The impeller according to claim 1, wherein both of the first segment and the second segment are made of a fiber-reinforced plastic.
 5. The impeller according to claim 1, wherein both of the first segment and the second segment are made of a metal material.
 6. The impeller according to claim 1, wherein the impeller is fixed to the rotary shaft through the first disc portion of the first segment.
 7. The impeller according to claim 6, wherein the first segment is made of a metal material and is fitted to the rotary shaft with an interference.
 8. The impeller according to claim 6, wherein the first segment is made of a fiber-reinforced plastic and is fitted to the rotary shaft with a bonding agent.
 9. The impeller according to claim 1, wherein a film made of a metallic salt is provided on a surface on which the bonding layer is to be provided, of each of the first segment and the second segment each made of a metal material.
 10. The impeller according to claim 1, wherein a mechanical fitting structure is provided between the first disc portion of the first segment and the second disc portion of the second segment.
 11. A rotary machine comprising the impeller according to claim
 1. 12. The impeller according to claim 2, wherein the impeller is fixed to the rotary shaft through the first disc portion of the first segment.
 13. The impeller according to claim 3, wherein the impeller is fixed to the rotary shaft through the first disc portion of the first segment.
 14. The impeller according to claim 2, wherein a film made of a metallic salt is provided on a surface on which the bonding layer is to be provided, of each of the first segment and the second segment each made of a metal material.
 15. The impeller according to claim 2, wherein a mechanical fitting structure is provided between the first disc portion of the first segment and the second disc portion of the second segment.
 16. A rotary machine comprising the impeller according to claim
 2. 17. A rotary machine comprising the impeller according to claim
 3. 